In a conventional injection molding method in which injection molding is performed for each cavity in succession by using a multi-cavity hot-runner mold having a plurality of valve gates, a valve for a first cavity is closed after the filling into the first cavity is finished, and at the same time a valve for a second cavity is opened to perform the filling into the second cavity. For a third and the succeeding cavities, injection molding is performed in the same way.
However, the aforementioned molding method has a problem in that a surface sink mark and the like are produced in the appearance of a product. Also, it has a problem in that a large mold clamping force is needed to completely fill each cavity.
Accordingly, an object of the present invention is to provide an injection molding method for performing injection molding for each cavity in succession by using a multi-cavity hot-runner mold, wherein a surface sink mark or the like is not produced in the appearance of a product.